This invention relates to circuitry for electrical arc suppression.
This invention was made with government support under Contract No. W-7405-ENG-36 awarded by the U.S. Department of Energy. The government has certain rights in the invention.
When an ion beam source is operating, small points of conductive material can develop on parts of the ion gun beam source and particularly on the plasma grid of the ion beam source. When this happens, the potential for increased current from those points can occur when the plasma is present. Enough current can flow through those sharp points or microdefects to release gas that can cause other areas on the ion beam source and the grids that are marginally arc stable to become arc sources themselves. This positive feedback can cause massive electrical arcing to occur. The electrical arcing can cause material to be vaporized, resulting in evaporation of impurities as well as ejection and deposition of physical material onto the substrate, creating defects in film being coated.
Therefore, there is a need for a means for arc suppression in ion beam sources. There is a particular need for a means for arc suppression in flow through ion beam sources such as that disclosed in U.S. Pat. No. 5,601,654 issued Feb. 11, 1997.
It is an object of this invention to provide a means of electrical arc suppression.
It is another object of this invention to provide an apparatus particularly suited for suppression of electrical arcing in ion beam sources.
It is a further object of this invention to provide a means for electrical arc suppression in flow through ion beam sources.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims which are intended to cover all changes and modifications within the spirit and scope thereof.
To achieve the foregoing and other objects, and in accordance with the purposes of the present invention, as embodied and broadly described herein, there has been invented a circuit for suppressing electrical arcing in an ion beam source or other plasma devices. The arc suppression circuit of this invention detects current rises on ion beam source grids which cause arcing, disconnects the current flowing to the grid, and grounds the ion beam source to allow excess charge and current to be drained from the ion beam source rather than letting the charge and current arc on the grids of the ion beam source. A novel timing sequence is used for activating and deactivating the arc suppression circuitry to prevent shorting out of the power source. The arc suppressor circuits of this invention can be used on devices other than ion beam sources or plasma devices.